Geostationary high altitude platform

ABSTRACT

A geostationary platform is held afloat by a superpressure balloon. A suitable altitude is 25 km. The craft carries electrohydrodynamic thrusters, to overcome winds, held within a scaffold. Sensors determine position, velocity, acceleration and vector. A CPU performs instructions for station-keeping or navigation. A communication system is included to, inter alia, receive instructions from the ground. The craft carries a payload for observation and transmission, cradled in a temperature-controlled chamber. Power to the platform is transmitted in the form of electromagnetic waves (with suitable frequencies including microwaves of 2.45 GHz or 5.8 GHz) from a ground-based transmitter to a receiving antenna on, or affixed to, the balloon which converts the electromagnetic energy to direct current. A step-up voltage converter increases the voltage as required. A ground station monitors craft position and operational efficiency by radar to help ensure safe takeoff, operation, and landing of the craft.

FIELD OF THE INVENTION

The invention relates to the field of telecommunication, specifically tohigh-altitude platforms used for observation and transmissionactivities.

BACKGROUND OF THE INVENTION

The global high-altitude infrastructure which makes possible our moderndigital, wireless world with services such as mobile phones, internetand GPS heavily utilizes space satellites in orbit. Satellites canobserve large sections of the Earth at one time and instantaneouslytransmit signals over vast distances and across the planet,circumventing mountains and tall buildings. The satellite industry isworth over $200 billion dollars a year and is growing rapidly.

Constructing satellites and their payloads can cost millions of dollars.They are made extremely durable and resilient to, inter alia, survivelaunch force. Further, they are currently designed and built with themindset of “launch it and forget about it”, because there is nocost-effective way to retrieve a satellite or do any physicalmaintenance or upgrades.

Launching a satellite is even more expensive: $100 to $300 milliondollars each. Historically this was only performed by governments. Now,many private organizations and ambitious entrepreneurs are startingprivate space companies with the hope of creating improvement, but thecosts are still huge.

The satellite business is also getting dangerous. Space orbit is gettingcrowded, with dozens of countries currently operating over 1,200satellites (not to mention abandoned ones) and over 60 thousand piecesof space debris. Further, with no international agreement on orbitalpaths, collisions happen, and they can be devastating. Astronauts on theInternational Space Station frequently have to go into their “lifeboats” during impacts.

BRIEF SUMMARY OF THE INVENTION

The invention, according to one aspect, presents a solution in the formof an alternative to satellites and drones: a high-altitude balloonplatform that can stay up in the sky, in one place, for indefiniteperiods of time. The balloon craft holds up a payload to allow for theperformance of the desired high-altitude services, just as aconventional satellite or drone would facilitate.

The present invention includes a lightweight superpressure ultralong-duration (ULD) high-altitude balloon (HAB) platform for deploymentto a target altitude. The altitude chosen in this embodiment is 25 km.Electrohydrodynamic (EHD) thrusters are presented to maintain positionby overcoming stratospheric winds. Critical to maintaining position is acontinual supply of electrical power to operate the on-board propulsionsystem. A solution is to deliver power wirelessly to the craft from aground-based transmitter. Microwave energy, not heavily attenuated bythe atmosphere, can be provided remotely from a ground-based generator(magnetron, klystron, etc.) and steered electrically with an antennaarray (phased array) at a designated frequency (such as 2.45 or 5.8GHz). A rectifying antenna (“rectenna”) on the bottom of the balloonconverts waves into direct current for on-board use.

Throughout this discussion, the environment in which the craft operateswill be described through reference to Cartesian coordinates inthree-dimensional space. Herein, the z-axis will refer to verticaltranslation above the Earth, regardless of latitude or longitude. Thevariables x and y axes may be used interchangeably to understandhorizontal position, either in the North-South or East-West directions.However, for simplicity, the terms North-South and East-West will beused more often than x and y, to ensure clarity.

The craft is launched from the ground and can fly into position at lessthan one g. The craft stays at the chosen altitude due to the buoyancyof the superpressure balloon. The craft will maintain lateral positionwith a series of re-engineered low-power electric thrusters which useair—not fossil fuels—to operate, thus not requiring any propellantrefuelling.

For safety and to allay fears, the beam can be turned off automaticallyif anything is in the area, while onboard batteries temporarily takeover. In another embodiment, multiple transmitters can be utilized, sothat some beams can be deactivated while objects pass through, whileother beams maintain continual power supply.

The embodiment shown herein is designed to operate at 25 kilometresaltitude, achieved by design of the size of the superpressure balloonshell, which will be disclosed further below, although the shape andsize can be varied to achieve an altitude higher or lower. The chosenaltitude has no lateral activity except for the occasional weatherballoon. The altitude is 10 kilometres above weather and air traffic,and 30 kilometres below the typical limit of atmospheric meteorpenetration. This altitude is chosen also for the advantage of minimalwind resistance, reducing power consumption and optimizing deviceperformance.

From this altitude, the craft, with its continual power supply from theground-based power transmitter, can provide a substantial cone of groundcoverage over one thousand kilometres in diameter, resulting in nearlyone million square kilometres range for observation and transmissionservices. Several duplicates of the craft, arranged at precise intervalsto create slightly overlapping coverage, can enable coast-to-coastcoverage.

The craft can be directed to ground in a controlled manner as requiredfor regular maintenance and payload upgrades or replacement. A regularground visit every 4 to 6 months is reasonable, given currentcapabilities of commercially-available superpressure balloons.

Value to Users

A geostationary balloon platform located at high altitude could offereconomically and strategically advantageous methods of data collectionand transmission compared to orbiting space satellites,telecommunication towers, unmanned aerial vehicles (UAVs) such asdrones, and other forms of high-altitude balloons. Such a platform asdescribed herein could provide high-demand services such ashigh-capacity wireless broadband internet distribution to remote andunder-serviced regions while also enhancing line-of-site propagationtransmission. Other potential applications include search-and-rescueoperations, disaster relief, national defence, border patrol,intelligence, surveillance and reconnaissance gathering and relaying,emergency communication restoration, remote sensing, surveying andmapping, forest-fire and other disaster detection, environmentalmonitoring, climate and science research, astronomy, meteorology, andeducation.

The platform could provide a relatively easily deployable, longduration, sustainable solution for many high altitude services valuableto both scientific and commercial endeavours. The platform offers morepower (kilowatts, and conceivably megawatts, instead of watts ormilliwatts), longer flight times (months instead of days or hours),stable position, minimal ground footprint (no long runways) compared tounmanned aerial vehicles (UAVs). The balloon is also easily movable to anew position, a significant advantage over telecommunications towers.The geostationary balloon can also offer uninterrupted service by meansof multiple balloons working collaboratively in a region.

The platform can be positioned at high-altitude, anywhere in the world,and deployed relatively rapidly.

Ultimately, the present invention may solve the problem of spacecrowding in a simple and more environmentally friendly way bytransferring operation from orbital space to the stratosphere, and notcontributing to the pollution of space launches and orbital debris.

Value to users includes: Resolving the serious and urgent problem ofover-crowding in space orbit; payload retrieval for repair orreplacement; relatively low cost, complexity, and risk; relatively rapiddeployment; no mechanical moving parts, relatively invisible to infraredsensing, minimal or no waste heat, relatively relaxed payload designconstraints; relatively invisible to observers at ground level; nofossil fuels, no waste pollution; will not interfere with air traffic,weather, or space activity during normal operation; and will not crowdthe operating region of the stratosphere.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic view of a system according to an exemplaryembodiment of the invention;

FIG. 2 is an enlarged view of the structure of encircled area 2 of FIG.1

FIG. 3 is an enlarged view of the structure of encircled area 3 of FIG.2

FIG. 4 is an exploded view of the structure of FIG. 3; and

FIG. 5 is an enlarged view of the structure of encircled area 5 of FIG.4.

FIG. 6 is a sectional view of the Earth, showcasing ground coveragerange (s) as a function of angle (theta) and Earth radius

FIG. 7 is a sectional view of the Earth, using craft height and Earthradius to solve for the angle (theta)

FIG. 8 is an extrapolation of FIG. 7, without the Earth

DETAILED DESCRIPTION

As shown schematically in FIG. 1, the system 20 comprises two primaryfacets: an air-borne craft 22; and ground-based components 24.

The functions and structures of the components of the air-borne craft 20are described in detail as follows.

Balloon

The craft 20 includes a superpressure balloon 26, as shown in FIG. 2. Asuperpressure balloon is a sealed, plastic cell that floats at aconstant density altitude, despite ambient temperature fluctuationsbetween day and night. Internal pressure of the lighter-than-air gas iskept at a greater value (‘super’) than ambient pressure at all times toensure buoyancy, without significant change in volume. Embedded ropesensure that the balloon volume is roughly constant at the targetaltitude (Grass, 1962). Helium is generally preferred as a lifting gasover hydrogen to prevent combustion.

Design of the superpressure balloon depends on various criteriaincluding atmospheric drag, operational efficiency, cost, materialstrength, and ease of manufacture. Balloon skin is typically made ofvery thin, lightweight, durable material such as Mylar or 1.5 milco-extruded LLDPE film. A sphere shape is preferred for superpressureapplications as the sphere retains the highest values of internalpressure for a given maximum safe stress on the material. Research inthe past two decades has shown that the elastica or pumpkin shape canalso be a viable alternative shape, from material strength anddurability perspectives

However, drag is a critical consideration when selecting optimal shapefor long duration flights. While a sphere is high in drag compared toelliptic shapes such as the dirigible or blimp, the sphere offers theadvantage of consistency in drag, in all three axes. A uniform balloonwill respond equally to wind forces in all three directions, includingdown and updrafts, without having to change direction to minimize drag.This approach will not burden the thruster and communication systemswith constant manoeuvres, or risking damage from twisting andcontorting. For the proposed station-keeping system described in thisstudy, based on uniformity of drag as a primary design consideration,the sphere is chosen for this specific embodiment.

Propulsion Mechanism

A propulsion mechanism is incorporated into the present design tomaintain lateral station-keeping against high-altitude winds, namely, aseries of electrohydrodynamic (EHD) thrusters 28. Such devices arelightweight, cost-effective, air-breathing thrusters. They possess nomechanical moving parts to help prevent against wear, fatigue, and riskof failure in the cold temperatures of the stratosphere. EHD technologyhas been well-understood for decades.

The EHD thruster 28 is a lightweight structure made up of a thin wire 30and a thick aluminum sheet 32, both arranged as triangles and heldtogether by a lightweight dielectric such as balsa wood. The designdepicted in FIG. 5 is based on Masuyama et. al. (Masuyama, 2013). A longwire (40 cm between balsa posts 34) 30 made of 35 standard wire gage(SWG) is charged to +/−40 kV relative to the grounded collector plate 32made of a coaxial sheet of aluminum. Optimal separation distance betweenwire and plate was found to be 23 cm.

With the application of high voltage (30 to 40 kilovolts), ambient airparticles are ionized at the emitter and accelerate toward thecollector, colliding with neutral particles to exchange momentum but notcharge. The ions recombine at the collector to complete the circuit, butthe neutral air molecules continue through the device, providing thrustin the opposing direction.

FIG. 5 illustrates a modified version of the Masuyama (Masuyama, 2013)design, with an additional emitter wire 30 to enable propulsion ineither forward or reverse direction. This novel feature can assist withsteering, balance, or stopping the craft, for travel and station-keepingpurposes. The wiring and programming should be created such that the“forward” emitter wire and collector/ground wires are activated togetheror alternatively the “back” emitter wire and collector/ground wires areactivated together, but never any other combination of these threeelements for risk of electrical failure, short, or wasted energy. Whenone of the two emitter wires of the thruster is engaged along with theground collector plate, then the thruster will be propelled in thedirection of the active emitter wire.

In this embodiment of the present invention, all thrusters are alignedon the scaffold such that they face the same direction. Thus, when allthrusters on all ladders of the scaffold are activated in the samedirection, then the craft will be propelled in that direction.Conversely, if some thrusters are activated in one direction while otherthrusters (on a different ladder or at a different position on the sameladder) are activated in the opposing direction, then the craft willperform a rotation or sway.

In use, a determination may be made to rotate or sway the craft based onits current position, vector, velocity, acceleration, or orientation.For example, the craft may need to be turned into the wind, orstraightened out from an angle or tilt, or may be experiencing strongerwinds at one vertical position than another, and different magnitudes ofthrust are required at different elevations to maintain verticalerectness.

Each individual thruster offers less than one Newton of thrust, but onlyweighs on the order of grams. The total number of thrusters needed toensure adequate station-keeping will depend on the force required tocounteract high-altitude winds, and is explained in detail furtherbelow.

Scaffolding

EHD thrusters require clear air flow in the front and out the back. Ascaffold 36 is presented in this embodiment of the present inventionwhich hangs down from the balloon 26 and carries a large complement ofthrusters 28. This scaffold consists of a series of ladders or trussesmade of lightweight material.

The scaffold can be enlarged at the base akin to an inverted pyramid.This inverted pyramid model provides aerodynamic advantages, since thethrusters are more spread out near the top of the balloon, which itselfis a source of drag. Therefore, a further spread out complement ofthrusters nearer to the balloon and at the top of the scaffold thanfurther away from the balloon toward the bottom of the scaffold, willallow the thrusters to help compensate and ensure that the balloon doesnot become warped or bent as it traverses, and does not fall behind andrisk adding strain to the craft and possibly tilt and thus misdirectionto the intended path of travel. In addition to an inverted pyramid, alarger complement of thrusters at or near the balloon, at the top of thescaffold as opposed to at the bottom of the scaffold helps place thecentre of mass further away from the balloon, so that it will not causedrag and potential tilt or misdirection.

The scaffold ladders 36 are attached to the balloon 26 by harnesses 38,secured to protrusions 40 emanating from the balloon 26. Suchattachments will need to be conducted in such fashion that the scaffoldladders do not twist and contort, but rather are secured from rotating.One way to do so is to include several harnesses attached to severalprotrusions for each ladder, ensuring the prevention of a z-axisrotation.

Additional embodiments of the scaffold include an upright pyramid inwhich the individual ladders emanate from a central spot on the bottomof the balloon, and fan out toward the bottom. At such a bottom could bea large platform. This design may be beneficial if a client required alarge platform or some form of large area activity at the bottom of theballoon. This design would also be beneficial if the constructor wantedto place the power receiving antenna away from the balloon, or at thebottom of the craft in this matter, or needed the power closer to theclient payload, or needed the payload above the receiver, or any otherpossible reason to have a large base.

Each ladder can house a number of thrusters, all facing the samedirection. In another embodiment, different ladders could be mountedperpendicular to each other so that a percentage of the total thrusterswould face “North/South” while the remaining set would face “East/West”to allow for a different form of control, in all directionssimultaneously.

In this embodiment, thrusters would be separated from each other alongthe truss by a minimal distance so that they do not interfere with eachother. In other embodiments, the thrusters might be directly connectedto one another to save space and thus mass.

Thruster disbursement and quantity can be increased or decreased as isdeemed necessary to account for different anticipated wind flows, dragresistances, or other parameters.

In one embodiment, the scaffold can be hollow to reduce excess massburden. Scaffold should at the very least have some decree of cavity toallow for electrical wiring, running from the thrusters (and any sensorschosen to be placed along the scaffold) up (or down) to the power supplyand voltage conversion components, located near the rectenna.

Rectenana

Energy transmitted wirelessly from the ground will be received onboardthe craft by a thin-film rectifying antenna (‘rectenna’) 42.

This thin film material can be affixed to the balloon by forming it ontoa rigid or flexible truss which is attached onto the balloon by straps,connectors, or some other method to the protrusions on the balloon.Conversely, the thin film rectenna may be directly imprinted onto theballoon skin by lithography. Other methods, both existing and yet to beconceived may be employed to safely and securely connect the rectenna tothe balloon. In another possible embodiment, the rectenna may be hungdown from the craft, so that it is carried below the thrusters, and/oron the bottom and sides of the client payload.

In yet another possible embodiment, the rectenna may also be carriedwithin the balloon skin, either affixed or hanging from the top, orsimply contained somewhere within. It may be found, however, that it ismore advantageous to keep the two technologies (balloon and rectenna)completely separate entities, for ease of replacement of one or theother, and to manage heat flow through the balloon. Such a decision isleft to the discretion of the manufacturer, and might be influenced bymany factors including, but not limited to: mass management anddistribution, angle of the power beam, and concerns of signalinterference against the communication system and client payloadoperations, among other issues.

A rectifying antenna (or “rectenna” for short) converts EM waves todirect current. A valuable primer on the technologies and design ofwireless power systems is provided by Shinohara (Shinohara, 2014). Therectenna, developed in the 1960s, consists primarily of an antenna,filters and Schottky diodes. The dipole antenna receives and convertsmicrowaves to direct current (DC), while the band-pass or low-passfilter minimizes unwanted signal. A Schottky diode rectifies the signalinduced in the antenna to produce DC power. A DC filter further refinesthe signal. The device then powers a load connected across the diode.Some rectennas have demonstrated 85% efficiency when converting anddelivering energy, showing DC power output densities of 1 kW/m² and DCpower-to-weight ratios of 4 kW/kg (Brown, 1984).

The rectenna may be etched on thin films to significantly reduce mass.Sheets of printed circuit can be industrially produced on rolls andunravelled prior to (or during, or after) balloon deployment. Thin filmrectenna components can be fabricated using flexible, cost-effectivematerials such as organic semiconductors.

Onboard Power Management System

Power received by the rectenna will not necessarily be of the voltagelevel needed by the EHD thrusters (on the order of 0 to 40 kV (Masuyama,2013). Accordingly, step-up voltage converters may be used to generatethe high voltages. These converters 44 will be placed near the rectenna,on the bottom of the balloon so that voltage is amplified while en routeto the thrusters.

Communication System

The craft will include a communication system 46 to transmit and receiveinformation which may or may not include instructions, to and from theground station. System can consist of, but is not limited to: atransceiver, capable of sending and receiving information, and atransmitting antenna, preferably of lightweight design.

There are many transceiver options available which are alreadywell-established within the high-altitude balloon industry. Transmissionantennas can include, but are not limited to phased array antennas, andall of the antennas discussed in the power transmission section, below.Many options are available for combinations of different transceiver andtransmission antenna choices, and the goal of the design is to allow theconstructor an ideal range of choices to best suit the particularcommunication needs of their embodiment, considering factors such as(but not limited to): transmission distance, power usage,signal-to-noise ratio, security factors (encryption, exclusively ofaccess to the communication EM beam), and many other possible factors.Frequency allocation for communication should be determined based onappropriate regional legislation governing electromagnetic frequencyspectrum allocation, and must also be carefully selected so as not tointerfere with the frequency of wireless power transmission.

The craft communication system must be capable of communicating with theground station radar facility to transmit craft health and status,position, vector and other information, and to ask for instructions whendeemed necessary by pre-programming, for course corrections, emergencylanding authorization, or other issues of importance. The ground-basedsystem is discussed further below.

Control System

The balloon system will be pre-programmed to operate autonomously, withthe goal of maintaining craft position by activating thrusters tocounteract winds. Programming can consist of computer instructionswritten into a CPU which when evaluating the position, vector, velocityand acceleration of the craft, send instructions to activate and/ordeactivate specific thrusters so as to change course and speed toachieve the desired position.

An on-board computer 48 including the CPU will evaluate all sensor datato determine if activation of certain thrusters is required toreposition the craft. If the computer system identifies itself astraversing laterally away from the origin point beyond a certainthreshold (such as the maximum detectable variation in GPS signal) thenthe appropriate thrusters will be activated in the opposite direction tocounter the flow. When the craft is near to the target destination, thecomputer will switch those same thrusters to operate in the reversedirection, to counter the forward thrust and slow the craft to a stop.

Sensors

The craft carries a complement of sensors 50 for a variety of functions.In this particular embodiment, individual ladders of the scaffoldhanging down from the balloon can each carry a compliment of sensors,uniformly-distributed up and down, in order to determine position,velocity, and acceleration of each ladder relative to one another, andto the craft overall, and to the point of origin where the craft willendeavour to remain. Also in this embodiment, an additional set ofsensors will be carried on board to determine if the craft has driftedaway from the origin point. This service will also require a referencepoint or service on which to base the decision of position. To that end,the present invention will require either collaborative efforts from aground station which can transmit a homing beacon, or some other form oflandmark to use as a reference point including, but not limited to, adistinct object (in the sky or on the ground or at the horizon), areference point in space, a GPS signal or series of signals, or someother means of localization. In this particular embodiment, sensors caninclude but are not limited to: accelerometers, magnetometers, GPSpositioning systems, thermometers, and altimeters to provide feedbackfor positioning and altitude. The goal of this particular complement ofsensors is to determine the above position, vector, velocity andacceleration conditions in order to guide the craft to the desireddestination. However, any additional sensors could also be included toassist with guidance as well as other functions. Any type of sensorscould be placed at any position on the craft to assist with theseprocesses including, but not limited to: on the balloon, the scaffold,the thrusters themselves, or the client payload compartment.

All of the sensor technologies and procedures discussed above arecommonly found in industry practice on high-altitude balloon craft.Accelerometers will measure proper acceleration (gravitational force) todetermine altitude and orientation, and coordinate acceleration,vibration, and shock. Accelerators are a well established technology,often used for inertial navigation systems for aircraft and missiles aswell as in tablet computers, digital cameras and some video gamecontrollers. Magnetometers determine the strength of the Earth'smagnetic field and will be used to confirm altitude and position. Globalpositioning systems (GPS) will evaluate longitude, latitude, altitude,and time acquisition. Temperature sensors can monitor equipment withinthe craft, but also air temperature outside the craft to confirmaltitude. Altimeters will measure atmospheric pressure, to furtherconfirm altitude.

GPS accuracy for civilian applications in the United States (forexample) offers a “worst case” pseudo-range (distance from GPS satelliteto receiver) of 7.8 meters at a 95% confidence level (DoD, 2008).Assuming this worse case, GPS sensors will detect when the craft hasexceeded this 7.8 m range in any given direction and thrusters willengage to return the craft to the origin, providing a minimum totalrange of motion of 191 m².

The ability of the craft to perform this precision flying will depend onthe consistency of force generated from each individual thruster unitupon activation. Research among various groups (Shibata, 2016, Masuyama,2013, Gilmore, 2015, Moreau, 2013, Koziell, 2011) has demonstrated thatEHD thrusters can generate a consistent amount of thrust for a giveninput voltage and current. Further work will be required to verify suchconsistency within the low-pressure and low-temperature environmentfound at high altitude, and the consistency of time delay betweenactivation of thruster and achievement of full thrust force, but theidea that electrohydrodynamic thrusters can offer precisestation-keeping is sound.

Automatic on-board systems could be given even greater control of theoverall balloon mission, such that the craft could independentlydetermine if it should descend to the ground in the event of a emergencyor problem such as loss of power, lack of communication, collision,impending collision, system fault, or some other problem. Override ofsuch protocols from ground is also a possible option, subject tomanufacturer desire and government regulations. The ground station canalso contribute to positional stability by monitoring the craft andoffering instruction.

Backup Battery System

In the event that there is a problem with, or an interruption to, thewireless power supply, or some reason that power cannot be suppliedthrough the wireless transmission system, then one possible embodimentof the craft (and a recommended feature) is to include a battery backupsystem 52 to provide temporary, emergency energy. This system canprovide energy to all, many, some, or a few of the components on board,such as the CPU, power conversion system, thrusters, communicationsystem (sending and receiving), sensors, and the client payload.

The CPU can be pre-programmed so that in the event of an emergency inwhich wireless power is inaccessible, the on-board battery complementwill be enacted, and will provide electrical energy to the system(s) ofchoice. The total amount of battery power desired, and the type ofbattery chosen (storage capacity, mass, recharge rate and number ofchargers possible) will influence how many batteries are to be carriedaboard the craft. Total energy demand will therefore influenceadditional carrying mass, and thus affect the design of the balloon andsubsequent components. Detailed description of the design process isincluded further below.

In one possible embodiment, the on-board complement of batteries can berecharged by the wireless power system, so that when the wireless powersystem is restored (if it can be) then the batteries will be replenishedfor the next instance when they are required.

In one possible embodiment, additional computer programming can beimplemented such that if the battery backup is engaged, or isoperational for a certain period of time, then the craft can bepre-programmed to change it's objective (such as maintain position) andcan instead take action to change position, return to a new position(such as the landing field), and can begin landing procedures. The craftcould go so far as to carry out a complete landing in the event of lossof wireless power transmission. Override of this emergency service couldbe possible from ground if the constructor so chooses. A lock could alsobe provided so as to ensure that once a certain stage of emergencyprocedure has take place (such as landing procedure has commenced andthe craft has reached a certain threshold distance from the ground) thenthe system cannot be overridden, if the constructor so chooses toimplement.

Heating System

For electrical equipment to perform efficiently and reliably, it isadvisable to operate equipment within its specified ideal temperaturerange, often found generally to be between 0 and +40 degrees Celsius andvarying for other more sensitive or more ruggedized equipment. Giventhat the craft will experience external temperatures of −60 degreesCelsius on its journey up into the stratosphere (which is the targetaltitude of this particular embodiment) as well as on its way down,along with low temperatures within the stratosphere itself, it isadvisable that sensitive electronics and equipment be housed incontainers which offer some degree of temperature control, through heatgeneration as well as encapsulation. The high-altitude balloon industryalready employs techniques such as insulated containers and heatingimplements to maintain a relatively warm temperature for theinstruments. Some embodiments can be as simple as Styrofoam containerswith or without small heaters. More complicated containing systems arealso possible, in some instances relying on a source of energy.

Given that the duration of missions may be much longer than traditionalballoon flights, and the prospect that enclosed electronics (CPU anddata cards, sensors and instruments, etc.) might not generate enoughwaste heat to maintain optimal environmental conditions, then onepossible embodiment of the invention would be to include lightweightinsulating containers and incorporate heating elements, utilizingelectricity to generate the precise amount of heat. Since electricalenergy is plentiful (given that it is transmitted wirelessly) and massis of prime concern when constructing a lighter-than-air craft, it isadvised that electrical energy be utilized rather than some other formof energy source such as fossil fuels, which would increase payloadmass, create an imbalance in mass from beginning to end of mission, andwould require more frequent landings to replenish supplies.

Cargo Hold

The function of the craft in this embodiment is to carry a clientpayload 54 to a target altitude to perform services, such ashigh-altitude observation, transmission, and telecommunicationactivities. To that end, the balloon platform must carry aboard a clientpayload. Such a payload is not hampered by the design and constructionlimitations imposed by the rigors of space launch and orbital travel,but must nonetheless contain certain measures of protection, namelyinclement weather and safety for landing.

If the client payload contains electrical equipment which is not alreadyruggedized for extreme environments, then the payload should most likelybe encased in a lightweight, temperature-controlled container which willensure effective and consistent operation of the client's electricalcomponents, as described in the above section on temperature management.Further, the container should also offer support for the potentiality ofaggressive impact with ground due to unforeseen rough landings orcollisions with any external elements. Such protection might come in theform of (but is not limited to) foam, springs, shocks, absorbing pads,or some other means of absorbing and/or redirecting the force of animpact to protect the equipment housed on and/or within the payloadcontainer.

All of the aforementioned payload containers should hang down from theballoon, a safe distance away from the thrusters and power receiver. Inone embodiment, the client payload can be housed in a container farbelow the thruster scaffold, as seen in FIG. 3. In other possibleembodiments, the client payload may be ideally suited (ie. small enoughand/or ruggedized enough) that it could be carried outside of aprotective container, and in another position, such as directly on theballoon itself, or within the thruster scaffold (at one position ordistributed throughout), or on the rectenna.

In the event of an emergency landing on water, one embodiment of thepresent invention would be to equip the payload compartment withflotation capability, to increase the potential for a successfulrecovery.

Parachute

In this embodiment of the present invention, the craft will carry one ormore parachutes, ready for deployment to safely lower certain elementsto the ground to reduce the risk of damage or injury. Such safetyprocedures are common practice with high altitude balloons. In thisembodiment, one parachute is accounted for in the mass budget.

In the event of an emergency, the craft may be forced to return to Earthrapidly and unexpectedly, and may not have the option of a controlledlanding. Alternatively, the client or operator may wish to returncertain elements of the craft to the ground in an expedited manner. Insuch a situation, the parachute should be deployed, either automaticallyor by manual control and override. In such an instance, the parachutewill be ejected from a storage compartment aboard the craft, as ispracticed on modern high-altitude balloon craft. Common practice if aballoon is popped and destroyed is for the parachute to deploy, allowingthe critical components to return safely to the ground for recoveryunharmed, as well as without causing damage or injury to any elements atthe landing site or along the journey downward.

Numerous parachutes can be stowed aboard the craft, to provide for arecovery of the entire cargo complement excluding balloon but includingthrusters, scaffold, sensors, rectenna, and client payload. Analternative embodiment would have additional parachutes to specificallyprotect each of the aforementioned items, or specific collections of theabove mentioned items.

Flight Termination Unit

In the event that the ground crew desired the payload or variouscomponents to return to the ground quickly, then an early termination ofthe mission would be possible by activating the flight termination unit.Such a device is also standard practice in the balloon industry, and canbe as simple as a wire draped over or wrapped around the primary supportrope that connects the balloon to the train of equipment below. The wirewill be connected to a power source, and when the power source isactivated, the wire will overheat, burning the supporting rope until itbreaks and severs the tie between the balloon and the rest of thepayload and components.

Recovery Beacon

In the event of an emergency landing, it would be advisable to include ameans for finding the downed craft and components.

In one possible embodiment, each section which is separately housed, orcould become separated from the main body due to its specific design andconstruction, could be equipped with a homing beacon that would transmitthe location of the component to ease in searching and recovering. Sucha beacon could be always-on, or could be activated either automatically(such as when the craft descends below a certain altitude) or manuallyby the ground crew or some other party with the appropriate authorityand control. The beacon could be of numerous designs that are in wideuse for applications such as search and rescue. Types of beacon couldinclude, but are not limited to: mobile phone, tracking transmitter,distress radio-beacon, transponder, hydrostatic release unit (HRU), GPSbeacon, high-precision registered beacon, emergency locator transmitter(ELT), location by Doppler (without GPS), and emergencyposition-indicating radio-beacon station (EPIRS or EPIRB), among others.

Although the models and particulars may vary, the function remains thesame; that of providing a signal over a prescribed distance of thelocation of the craft remnants in order to aid the search party inrecovery.

Use of emergency beacon technology may come with regulatory restrictionsand limitations in some regions. Choice of beacon may be affected bysuch factors.

The functionality of the ground based components is as follows:

Electrical Power Source

In order to transmit the amount of power required to the craft, theground station will require access to sufficient quantities ofelectrical energy. Such energy may be obtained from the local electricalgrid, upon solidifying the appropriate arrangements with energy powerproviders and the appropriate authorities, governing and regulatorybodies and other stakeholders in the region. Alternatively, power may bebrought to the ground station by means of portable, semi-portable, orpermanent industrial power generators including, but not limited to:diesel, natural gas, petroleum, portable industrial generators, marinegenerators, or heavy fuel oil generators. Renewable energy sourcesincluding solar, wind, geothermal or synthetic or bio fuels may beconsidered, so long as they are accompanied by the appropriate type andquantity of batteries for energy storage during non-harvesting times.

Ground Station Power Generator

The ground-based system will include a power generator 56, which couldoperate in numerous frequency ranges such as visible, UV, IR, near-IR,mid-IR, far-IR, radar or microwave, among others.

In this embodiment, a microwave generator is chosen, in particularoperating at a frequency such as 2.45 or 5.8 GHz. Such frequencies arewithin the industrial, scientific and medical (ISM) bands, and arechosen in this embodiment for their international acceptability.Microwave transmitting devices can be classified as either MicrowaveVacuum Tubes (magnetron, klystron, travelling wave tube (TWT), andmicrowave power module (MPM) or semiconductor microwave transmitters(GaAs MESFET, GaN pHEMT, SiC MESFET, AlGaN/GaN HFET, and InGaAS). Themagnetron, a well established technology, is widely used forexperimentation of WPT. It consists of a high-powered vacuum tube inwhich electric current runs along a heated cathode wire through aconductive anode cavity. Specially-sized holes in the cavity causeresonance, producing EM waves of the desired wavelength. The magnetronis small, compact, and cost-effective, with a long history of success(Brown, 1996, Wathen, 1953), and has been recommended for use in otherwireless power transmission applications (McSpadden, 2002).

Power Transmitter

A transmitter will propagate the electromagnetic power signal skyward ina reasonably confined manner so as to minimize size of transmitter,reduce waste power expenditure, and minimize the risk of harm elsewhereor atmospheric heating, among other possible motivations. Choice oftransmitter will be dependent on the frequency selected for powertransmission.

In some embodiments, a laser may be employed to generate electromagneticwaves or pulses in the visible, UV, IR, near-IR, and far-IR ranges,among others. In another embodiment, microwaves and radio waves could bethe targeted power transmission frequency ranges, namely between 1 and10 GHz. This particular embodiment will use microwave frequencies, withoptions presented for 2.45 GHz and 5.8 GHz. Thus, a microwave generatoras well as a large antenna for transmission will be required for thisembodiment.

Many antenna options are available including, but not limited to: wireantennas such as short dipole, dipole, half-wave dipole, broadbanddipole, monopole, folded dipole, loop, cloverleaf; as well as travellingwave antennas such as helical, yagi-uda, spiral; reflector antennas suchas corner reflector, parabolic reflector and/or dish; microstripantennas such as rectangular microstrip and/or patch, planar inverted-fantennas (PIFA); log-periodic antennas such as bow tie, log-periodic,log-periodic dipole array; aperture antennas such as slot, cavity-backedslot, inverted-f, slotted waveguide, horn, vivaldi, telescopes; otherantennas such as NFC, fractal, wearable; and any additional unmentionedantennas.

In addition to individual antennas, numerous antenna arrays (eitherparasitic or driven) are viable options for wireless power transmissionincluding, but not limited to all of the aforementioned antennascombined into arrays, as well as phased arrays, retrodirective arrays,smart antennae, interferometric arrays, and Watson-Watt/Adcock antennaarrays.

Numerous antenna arrays have already been proposed for wireless powertransmission in the microwave range (Massa, 2013, Ren, 2006) whichinclude but are not limited to the phased array and retrodirective arrayantennas. The power transmitting antenna presented in this embodiment ofthe present invention is a phased array antenna, composed of a series ofantenna elements, each of which has a phase shifter.

Beam steering is accomplished by changing phase slightly for eachelement, in succession. The main beam points in the direction of theincreasing phase shift. The overall signal is amplified by constructiveinterference, while beam sharpness is improved through destructiveinterference. A phased array antenna system laying flat on the groundwill provide up to 120 degrees of transmission in azimuth and elevation(out of a possible 180 degrees) or expressed as a maximum 60 degree tiltin a target direction. Steering occurs electrically with no mechanicalmoving parts, allowing for rapid direction adjustment, effectiveoperation in extreme and harsh environments, and reduced wear oncomponents.

An additional transmission option for an alternative embodiment of thepresent invention is the retrodirective array antenna whichautomatically transmits microwave power (or any signal) back in thedirection of the pilot signal without prior knowledge of the pilotsignal origin. A signal can be sent down from the balloon craft to serveas the incident pilot beam, and the retrodirective array on the groundcould automatically return power in the direction of the originalsignal. This requires less computationally intensive algorithms orhardware to achieve significant transmission. Retrodirective arrays areof growing interest due to their relative simplicity compared tophased-arrays. A demonstration of the effectiveness of retrodirectivearrays as power transmitters has been provided by Mankins (Mankins,2014).

Ground Communication System

In order to communicate with the craft, the present invention willinclude a ground station 58 possessing a radar system including (but notlimited to) a transceiver and an antenna, plus a CPU and interface tomonitor the craft, and issue override instructions as needed. Thecommunication system will also include a radar system to detect andmonitor the craft, as is commonly employed in radar applications overlong distances for military and aircraft logistics.

Such a ground station may be adapted from existing processes andprocedures for ground-based facilities that communicate with aircraft,drones, and space satellites. A ground station then may already be inexistence, and therefore purchased, or alternatively rented or leasedfor the duration of the operation of the craft.

Conversely, a station may need to be constructed or modified which willrequire acquisition of land, permits, public disclosure, and design,construction, and operation of such a station with all appropriateaccompanying parameters including (but not limited to) physicalconstruction and insulation, electrical power, utilities, safety,security, road access, comfort and convenience for human occupants, andcorresponding inspection protocols and procedures as would accompany anytypical construction project of a housing or workplace structure of thisnature.

Power Transmission Station

Transmitting wireless power will require an infrastructure to house andsupport the transmitting antenna, which may or may not be incorporatedinto the communication system. As a separate entity, the powertransmission station will require the use of a plot of land of asuitable dimensions to house the transmitting antenna with excess spaceas is required to prevent energy leakage to the nearby surrounding area.The station will also require a physical workspace for human occupants,power facilities, utilities, security, living quarters, maintenance andcleaning supplies and tools, reserve and backup equipment and suppliesand their corresponding storage facilities, and general storagefacilities, as would be anticipated with any similar remotely-basedoperation requiring high power output such as the Arecibo observatoryand radio telescope in the municipality of Arecibo, Puerto Rico.

Operational Considerations

In the event of an emergency with the craft, in which a change becomesnecessary for craft position, altitude, direction or some other aspect,then the CPU can be programmed to automatically carry out a pre-ordainedchange, or receive instructions from the ground (either original oroverriding) to make a change of craft behaviour.

Possible emergencies that might occur include, but are not limited to:failure from external factors such as inclement weather, high winds,excessive heat or cold, natural disasters (eg. volcano, volcanic ash,hurricane tsunami, or typhoon), collision with foreign object (eg.aircraft, or other human-made artefact, animal or bird, terrain,space-borne phenomena such as asteroid, meteor, space debris), externalattack (eg. missile, plane, explosion shrapnel, or other weapon orcombative effort); and failure from internal factors such as the failureof any one component or collection of components (temporary, requiringeither physical or remote intervention by humans, or permanent) whichleads to a critical failure in the craft ability to carry out themission, requiring specific change in activities.

Possible changes in activities that might be required of the craftinclude, but are not limited to: changes in position or course,direction, velocity, acceleration, or altitude. A craft may beprogrammed to automatically travel to a new or previous location, toland, or to sever the connection to the payload and drop it, viaparachute, to land or sea. The users or clients may be so inclined to doso for matters of sensitivity or security of the payload, itsinformation, position, capabilities, or other sensitive factors.

Details of the various threats, and the proposed programming required toovercome these challenges, are presented next.

Beam Avoidance

A beam of wireless power may be of substantial energy density whichcould potentially inflict harm on biological tissue if exposed, eitherdirectly or indirectly, for a certain period of time. Because differentembodiments of the present invention may call for greater or lowerdegrees of energy intensity, it is in the domain of the constructor toensure adherence to all legal and regulatory matters. Safety to life,particularly human beings, is of paramount importance, and the presentinvention should be constructed with safeguards in place to ensure thatoperation does not lead to harm.

To that end, in the event that objects approach or enter the path of thewireless power beam, the present system will be equipped with a means ofensuring that no harm comes to that passing craft, person, bird, animal,or other object, on an automatic and ongoing basis which does not causeundo wear or burden on the system, or lead to early failure or need ofrepairs. In the present embodiment, the invention is presented with ameans of automatically turning off the power beam in the event of apassing object, to guarantee that no harm comes to that object.

In this embodiment, the ground communication system, which will beequipped with radar to track the craft's position (as discussed indetail elsewhere) will also utilize that radar to track other objects inthe sky near to the beam. In the event that this radar system finds anobject coming into range of the beam, then the ground station computerwill determine how long until the object is within range of the beam,and terminate power transmission. The radar will indicate when theobject has passed by the danger zone, and inform the computer, whichwill then reactivate the power beam.

In order for the craft to continue operation while the beam has beenterminated, onboard backup batteries will be required on the ballooncraft to ensure continued and uninterrupted functionality. In thisembodiment, additional protocols may be put in place, such that thecraft's CPU may be programmed to take emergency actions if power is notrestored within a certain amount of time, such as (but not limited to)travel into the wind, either before beam termination or after, in orderto give the craft time to loft back into the ideal position; return to acertain position; begin landing procedures; execute a complete landing.

An alternative embodiment would be to operate multiple ground stations,each with their own independent power transmitters. Any power beam couldbe deactivated while an object passes through its range, while anotherbeam or multiple other beams located at a safe distance away would beactivated in the original beam's place, thereby ensuring a continualsupply of power to the craft without endangering passing objects, andnot requiring the same extent of on-board batteries for energy storage.Deciding whether to include this aspect of the invention will depend onmany factors including, but not limited to, costs of ground stations,power transmitters, electricity rates, land acquisition ability, andvarious permits and regulations, in contrast to the costs andcomplexities of additional battery carriage.

Harsh Environment

The balloon craft will operate in a harsh environment. The journey tothe cruising altitude in the stratosphere can subject the craft totemperatures that range from 30 Celsius to negative 60 Celsius. Toensure that all components function optimally in these conditions, allphases of the design will be put through realistic computer simulations.Modelling will demonstrate the durability and survivability of theballoon and scaffolding structure, as well as thruster effectiveness, inthese extreme cold conditions with strong high-altitude winds. Aparticular advantage of the geostationary balloon is that there are nomechanical moving parts. The propulsion system operates by the transportof air by electric means, so there are no rotating or turning partswhich risk freezing and malfunctioning. All components which aretemperature sensitive will be kept in climate-controlled containers toensure optimal performance.

Natural Disasters

The natural world can wreak havoc on any technology, and the balloon,despite its lofty position safely above clouds and air traffic, is stillno exception. The balloon is susceptible to volcanic ash which can riseup to the intended operating height. The balloon would need to be movedwell out of the way of the ash cloud for as long as it takes for thedust to literally settle, which could be on the order of days, or weeks,or in extreme cases, months. During that time, the balloon will likelyfail to provide all of its intended services to customers but therewould also be an unavoidable loss of business for all other competingforms of telecommunication such as satellites, drones or telecom towers,whose data transmission beams could also not penetrate the thick volcanoash. Protocols would need to be in place to ensure that in the event ofa volcano eruption, a balloon of the contemplated type wouldautomatically travel to a safe distance to avoid physical harm, andinform ground control of its position, its actions, and its currentoperational efficiency. Efforts must be made to minimize disruption tocustomer service, such as adding additional balloons to the periphery orusing alternate technology platforms altogether.

Space Threats

Meteors and space debris can be deadly if they strike a balloon. Whilemeteors are known to combust and dissolve at around 60 km altitude,there is still a risk, however small, of one getting through, or of apiece of man-made debris in space falling to the Earth. Probabilities ofcollision are based on the frequency of meteor events, and the amount ofspace that a balloon takes up in the sky. Estimates for a meteor strikeof a commercial airplane in transit range between 4 and 10 percent forone incident over the course of 20 years. However small the probability,all efforts should be made to develop a contingency plan. It iscontemplated that it will be advantageous to operate two balloons in agiven region for each paying customer, thereby ensuring that in theevent of failure of any one craft (such as from a meteor or space debriscollision event), there will still be a fully functioning craftoperating nearby to ensure uninterrupted continuation of service.

Collision/Attack/System Failure

In the event of any other form of collision such as contact with anairplane, helicopter, drone, balloon, bird, other animal, or naturalobject during ascent or descent, or in the event of an attack (missileor other propelled attack), the balloon craft may be damagedsignificantly or critically disabled. The balloon control system must bepre-programmed with the ability to evaluate its own condition, transmitsuch information to ground control to receive instructions, and also beable to make appropriate decisions autonomously, such as through anemergency landing or parachute deployment.

Emergency Landing

The balloon should be able to receive instructions from the commandcentre to execute a controlled emergency landing. The balloon systemshould also have the ability to carry out such a decision and actionautonomously if needed in the event of a fatal emergency and a loss ofcommunication from the command centre. If the balloon sheath itself ispopped, then the system should automatically deploy parachutes to ensurethat the payload is recoverable upon returning to ground. Thrustersshould be operable at all times to control the craft during descent, andto assist in landing at a desired area. The payload compartment willtransmit location at known but secured frequencies, to ensure timelyrecovery of the contents which will be locked safely inside. Use of landfor the landing zone should be negotiated in advance, and appropriateresources should be ready on standby in the event of unscheduled landingas well as for normal maintenance landings, including by not limited toemergency personnel, vehicles, tools, equipment, replacement componentsand appropriate representatives of the client.

High Altitude Debris

All efforts must be made to fully determine if any threats exist to theballoon and payload within the theatre of operations, the stratosphere.Potential threats such as ice, dust, or ionized particles are consideredextremely unlikely, but must nonetheless be carefully examined andevaluated, and potential solutions and fallback scenarios must bedeveloped. In the event of such an unexpected occurrence harming orincapacitating the craft, all of the above precautions and emergencyactions should take place.

Balloon Failure

High-altitude superpressure balloons currently have a life expectancy ofsix months at most, given the severe pressures they undertake andextreme environments they operate in. A balloon of the present type isexpected to operate longer because it does not partake in constantaltitude adjustments. However, balloons are expected to fail andredundancy plans must be in place to account for such eventualities. Aminimum of two balloons should be parked in the target vicinity, toensure that when one fails or is on the verge of failing, it can bebrought down for repair or replacement, while the other balloon remainsin the sky to ensure continuation of service. In the event that aballoon fails unexpectedly, emergency landing protocols will beinstituted which involve payload detachment from the balloon andparachute deployment for safe landing and recovery of cargo.

Thruster Failure

In the event that one or more thrusters are damaged or becomeinaccessible or unreliable, it may be decided by the ground crew toreturn the craft to ground (or to a place where humans or appropriateinstruments can physically operate on the craft) for inspection, andpossible maintenance. In one possible embodiment, the craft may beautomatically programmed to return to Earth in the event of a certaindegree of thruster failure (such as a specific count of unreliablethrusters).

Thruster health may be monitored by instruments either on-board thecraft, at the ground station, or at some other location, such as (butnot limited to) power gauges that measure how much electrical power isconsumed by a specific thruster, and/or by a CPU which compares theamount of electricity transmitted to a certain thruster, against changes(or consistency) in position, velocity, acceleration, rotation, vector,or vertical alignment.

Power Transmission Failure

If the balloon should fail to receive power from the ground station forany reason, protocols must be in place so that the balloon can a)transmit the problem to ground station, b) continue operations for a setperiod of time depending on available battery storage, and c) travel toa designated region of the sky and/or initiate a controlled emergencylanding. Depending on the level of activity of other balloons in theregion, protocols could be in place for a balloon to receive power froman adjacent transmitting ground station, thereby letting two craft sharea communal power source for a temporary period of time.

Failure of Communication

Constant communication between the balloon and the ground station willbe maintained to ensure consistent service and peak operationalefficiency. In the event of a communication failure but not a powerfailure, protocols will be in place to decide what steps, if any, totake next. General protocol will be to allow the craft to function withthe existing power beam for a set period of time, but if the craftcannot confirm that it is receiving power, it will be required toexecute a return to a predetermined receiving point to attempt tore-establish communication. Failing this reconnection, the balloon willbe pre-programmed to execute a controlled landing.

Control Failure

If autonomous craft control should be lost and emergency override byground control fails, the balloon could drift away from target and intoforeign territory. In such a case, protocols must be in place to ensurethat local partners can take control of the balloon. An importantfeature for many nations will be the reassurance that they can overridethe balloon if it happens to drift into their sovereign airspace. Afurther safety precaution must be in place to ensure override control.

Payload Failure

If a problem should occur with a customer payload requiring hands-onmaintenance, two safety features implemented in advance will avoidservice interruption. First, in one embodiment of the application of thepresent invention, two or more copies of the payload shall be deployedin advance to the same altitude, either aboard the same balloon or on asecond balloon cruising nearby, to ensure continual operation of theclient service in the event that one payload fails. Second, the balloonwith the failed payload will be sent for immediate landing, where thepayload can be repaired on the ground at the discretion of the client,while the second balloon (and possibly additional balloons) will stillbe in the sky in the same general vicinity to continue operations, foruninterrupted service. At the discretion of the manufacturer and theclient, additional payloads may be placed on stand-by at the launchsite, in the event that a replacement is needed rapidly.

Freezing

Appropriate precautions should be taken in advance of any component ofthe balloon craft suffering either from exposure to low temperatures(−60 Celsius) or from temperature fluctuations, since the craft isexposed to varying conditions during ascent and descent (−60 to +30Celsius). Throughout the entire balloon craft there are no mechanicalmoving parts, which greatly improves the durability of the entiresystem. Further, any sensitive electronic equipment is secured within atemperature-controlled payload container, protecting it from the naturalelements. Nonetheless, if any equipment should fail due to temperature,the balloon can follow the protocols above to execute an emergencylanding for repair or replacement.

Detachment

In the event that any individual component of the balloon becomesdetached and free-falls, emergency parachutes will deploy. If the entireballoon is lost due to damage or unforeseen circumstances, the primarypayload and scaffold ladders will separate by explosive means or flighttermination units and deploy individual parachutes, for a safe landingon ground. All major components should have tracking equipment for quickand easy recovery, and identification markings instructing any amateurbystanders who to contact.

If a component falls from the craft which is somehow not secured to aparachute, or if a parachute fails, then protocols should be in place toensure timely recovery of the components, restitution for damagesinflicted, and reassurance of the public well-being.

Loss of Craft

In the event of an unscheduled, emergency, or crash landing, thereexists the possibility of a total loss of payload. Insurance policiesmust be determined in advance to determine who will be responsible forpaying the cost of replacing the lost equipment and resources. In theevent that all backup balloons suffer a fate that leaves the customercompletely without service, then such policies must also account forrecompense of client losses.

Storage

Spare balloon kits will need to be stored at strategic locations nearclient service locations, in preparation for replacing any lost balloonsin operation. Should an active balloon fail and need to be brought down,emergency crews must be ready on stand-by to deploy the stored balloonwith the client payload at a moment's notice. Storage facilities must besafe and secured. In the event of fire, flood, earthquake, otherdisaster or political unrest, deployment of reserve balloons must not beat risk, and all efforts must be made to ensure that backups are readyfor deployment at all times and against all possible adversity.

Detailed Design Considerations

In order to integrate the various components described above, amethodology is now provided in detail. This process will first focus ondesign of the balloon and thrusters, followed by considerations requiredfor the ground station. Choices for balloon volume, quantity ofthrusters, and size of rectenna will all impact one other in aniterative process. The final mass budget is determined through aniterative examination of these components. The top priorities for designinvolve selecting two critical factors which may be client-specific andcould vary from one embodiment to another: (1) the payload mass, and (2)the cruising altitude. Both must be selected for varying criteria, andwill be chosen first, below, before moving to a detailed design.

Considerations for Selection of Payload Mass

The total mass required to be carried aboard the balloon (clientpayload, instruments and sensors, CPU, number of thrusters, etc.) willinfluence all subsequent design decisions. An initial mass for aprospective client application is selected as 50 kg (110 lbs), a valueoften used for small satellites. A demonstrative example is the NASAModular Common Spacecraft Bus (MCSB) used with the LADEE (LunarAtmosphere and Dust Environment Explorer) spacecraft (Elphic, 2014,Kuroda, 2014). Additional payload for the craft will include sensors,controls, internal wiring, parachute, and flight termination unit. Suchequipment for high-altitude balloons can collectively weigh as much as 5kg for small and short-term high-altitude balloons. We have selected asafety margin of 4 to arrive at an estimate for the mass of 20 kg forthese components in this embodiment. The total mandatory mass to belifted in this embodiment will therefore be 70 kg. This mass might belarger or smaller for any constructor's particular implementation, butthe value will be retained in this embodiment for the purposes ofdemonstrating the steps required to determine all craft parameters,based on an initial mass. That design process is detailed throughout thenext section.

Considerations for Selection of a Cruising Altitude

The preferred flight altitude is chosen next. Selection criteria forchoosing an optimal cruising altitude includes, but is not limited to:(i) minimizing or eliminating exposure to weather or the ionosphere,(ii) avoiding air traffic, and (iii) minimizing energy expenditure.Additional criteria may come to light which will also affect the choiceof cruising altitude including, but not limited to, client preferencefor a greater or lesser cone of coverage, greater or lesser resolution,or security concerns.

For long duration operation at constant position, the craft should bepositioned high above any possible inclement weather to ensure operationamong consistent wind conditions. Low-level stratus clouds produceprecipitation at or below 2 km (6,500 ft). High-level cirrus cloudsproduce localized precipitation and can reach heights of 6 km (20,000ft).

Modern air traffic is commonly located near 36,000 ft (6.8 miles or 11km) with a historical separation distance between craft of 2,000 ft. Analtitude far from this region is preferred for balloon operation. Thelowest ceiling of operation is therefore 11 km, given by air traffic.

The upper ceiling of operation is the ionosphere, for which the “D”region begins as low as 50 km. Ionized particles can detrimentallyaffect on-board sensors and propulsion system, especially ion-basedones, so this region should be avoided. Some balloon experiments haveachieved altitudes of 50 km but more common altitudes for balloonflights are notably lower, such as the Raven Aerostar superpressureballoon built for NASA which maintains a constant float altitude of110,000 feet (20.8 miles or 33.5 km) (Brooke, 2005) and the Super-TIGERat William's Field, Antarctica which cruises at 127,000 ft (24 miles or38.7 km) (Binns, 2014), well below the ionosphere threshold.

In the range between air traffic and ionosphere, cruise altitude ischosen for minimal wind drag, equal to the drag force (F_(D)):

F _(D)=½ρu ² C _(D) A  (1)

Drag coefficient, (C_(D)), depends on many factors including shape(Grass, 1962) and the Reynolds number. Due to its isotropic shape, asphere would have a uniform drag coefficient independent of winddirection and angle of attack. For spherical balloon shapes, therefore,the primary consideration for drag would be the Reynolds number. Atstratospheric flying altitudes, Reynolds numbers for balloons are around10⁴ to 10⁶. C_(D) for a sphere is relatively constant at 0.47 in fluidmediums with Reynolds numbers between 10³ and 10⁵, with higher Reynoldsnumbers yielding lower or equivalent drag coefficient values. Thus, forthe air mass range of interest, 0.47 can be taken as a conservativemaximum constant value for C_(D) for the proposed balloon system.

By considering air density (ρ) and wind speed (u) at various altitudesfrom meteorological data, the uniform drag coefficient of 0.47 andcalculating the corresponding surface area (A) of the superpressureballoon within the range of altitudes, the lowest maximum of averagewind force was found to be at a height of 25 km. Therefore this waschosen as the optimal altitude for a geostationary platform in thisstudy to minimize energy expenditure. Though this altitude is mostefficient for power consumption, the versatility of the proposed craftwill allow for other altitudes as needed to best suit the desiredapplication.

Table 1 presents the atmospheric conditions found at the targetaltitude.

TABLE 1 Atmospheric parameters (data obtained from (Randel, 1992))Parameter Value Units Altitude chosen above sea level 25,000 m Ambienttemperature −51.60 Degrees Celsius Force of gravity 9.73 m/s² AbsolutePressure 2,549 N/m² Atmospheric density 0.004008 kg/m³ Mean zonal winds(at 40° latitude) 12.36 m/s

Ground Coverage Range

The span of ground coverage for the high-altitude platform is dependenton the altitude of the craft and the radius of the Earth, as seen in thefollowing formula:

s=rθ  (2)

where s is the arc length across the Earth (representing the diameter ofthe cone of coverage), r is the radius of the Earth, and θ is the degree(in radians) between the two ends of s, as seen in FIG. 6, which shows adiameter (s) of the cone of coverage and is found with the angle betweenthe diameter ends (½ θ) and Earth radius (r).

In FIGS. 7 and 8, the circle represents Earth. From FIG. 7, a lineextending from the Earth centre (vertex of where both r lines meet)equidistant apart of each r, and up to the height of the craft, willcomprise the sum of the radius and the craft altitude, “r+h”. This lineis represented in FIG. 8. The line which is tangent to the circle fromthe end of the angled r to the top of “r+h” is at a right angle to theangled r.

The value of half of θ is found with the following calculation:

$\begin{matrix}{{\cos \left( {{1/2}\mspace{11mu} \theta} \right)} = \frac{R_{E}}{R_{E} + {Altitude}}} & (3)\end{matrix}$

From the target height of 25 km, based on an assumed Earth radius of6371 km to deliver an angle(θ) of 0.176889613 radians, the maximumcoverage radius would be 565 km (from diameter of 1,127 km), providing acone of coverage of 997,493 km² (just under 1 million square kilometres)for observation and transmission services. A series of balloons placedat relatively uniform distances apart (approximately 1100 km apart each)could collectively provide uninterrupted telecommunication connectionacross entire nations or even continents. A detailed link budget foreach craft would depend on the various electronic components selectedand power demand.

Design of Balloon Volume and Mass

The target altitude dictates the volume necessary for the superpressureballoon, thus volume is the first feature evaluated in determining thetotal balloon mass. Balloon lift is achieved when the buoyancy force ofan object exceeds the gravitational force on that object. A balloonreaches cruising altitude when the forces of buoyancy and gravityequate, such that:

ρ_(air) ·V _(object) =m _(total)  (4)

Total mass can be expanded to distinguish between payload mass(M_(payload)), balloon skin mass (m_(balloon)) and mass of the liftinggas (m_(gas)), chosen in this embodiment to be helium. The equation isthen further reduced to:

ρ_(air) ·V _(object) =m _(payload) +m _(balloon)+ρ_(gas) V _(gas)  (5)

As the balloon sheath is so thin compared to its other dimensions, thevolume of the contained gas can be taken as virtually equivalent to theatmospheric displacement by the outer volume of the balloon:

$\begin{matrix}{V_{object} = {V_{gas} = \frac{m_{payload} + m_{balloon}}{\rho_{air} - \rho_{gas}}}} & (6)\end{matrix}$

Density of the lifting gas (ρ_(gas)) is found by assuming ideal gasconditions with pressure and temperature at cruising altitude:

$\begin{matrix}{\rho_{He} = \frac{P_{ext} \cdot M_{He}}{RT}} & (7)\end{matrix}$

Inserting equation (7) into equation (6) produces an initial volume andthus radius and surface area of the balloon, as well as the mass ofhelium within. Balloon skin mass can be determined with the knownthickness and specific mass. For a balloon skin made of LLDPE (Grass,1962) the specific mass is 0.94 g/cm³. With surface area, the total dragforce (Equation 1, above) can be determined. A drag coefficient (C_(D))of 0.47 is selected, based on an ideal sphere in air.

Design of Thrusters

For a craft to maintain position in the face of high winds, the forcefrom the thrusters will be set equal to the mean zonal wind forcesexperienced at 25 km altitude, and for this embodiment at 40 degreeslatitude (Randel, 1992). The power needed for the thrusters can becalculated based on the known efficiency of a thruster unit. Thethruster from Masuyama et. al was capable of expending 13 W to provide0.335 N of thrust (Masuyama, 2013) (see Masuyama's FIG. 9-b), whichresults in a thrust/power ratio of 25.7 N/kW.

Knowing the total power required and the power efficiency per unitthruster, the number of thrusters required can be calculated. With athrust capability of 0.335 N per EHD thruster unit and a unit mass of0.24 kg (Masuyama, 2013), the thrust/mass ratio is found to be 1.396N/kg. The number of thrusters and their total mass can then becalculated. The lattice to support the thrusters will be presumed toequal 10% of the thruster mass, but choice of materials will determinethe precise mass.

Design of a Power Receiver

Brown et. al. (Brown, 1987) demonstrated a lightweight, thin filmrectifying antenna (“rectenna”) which could harness 4 kW of power per 1kg with 80% efficiency. Working backward from the amount of power neededto operate the thrusters (and the client payload) the minimum necessarysize of rectenna can be calculated. An appropriate margin should beassigned to account for various losses at edges and in lines. In thisembodiment of the present invention, the rectenna mass is found to be 92kg.

Craft Design Iteration

The design process for the overall craft now becomes significantlyiterative in a positive feedback loop. The increased mass from theaddition of thrusters, scaffolding, and rectenna will increase theamount of lift gas required and volume of the balloon, in order to riseto the same altitude. More volume means more surface area, whichincreases drag, requiring more thrusters to compensate. The added masswill require a balloon with more lift gas and thus of larger volume andsurface area, and so forth, making for a significantly large craft basedon only a small addition of payload mass. Final parameters are presentedbelow for the present design.

Mass Budget and Craft Parameters

Total thrust and various other parameters can now be determined, alongwith the mass for all components. Craft parameters are shown in Table 2.The masses for all components are shown in Table 3.

TABLE 2 Craft Parameters Category Units Known Craft Ideal Craft Balloondiameter m 81.6 39.8 Balloon surface area m² 5,233 1,245 Balloon volumem³ 284,700 33,060 Drag force N 7,524 1,791 Rectenna area m² 292 69Thruster units 22,461 5,347 Thruster power use kW 292 70 Proposeddesigns for center column (“Known Craft”): a balloon craft as describedin this paper with known EHD thrust-mass ratio based on (Masuyama,2013), compared against right column (“Ideal Craft”): an ideal ballooncraft with thrusters of superior thrust-mass ratio, conceptually basedon (Koziell, 2011).

TABLE 3 Mass Budget and Comparison Mass with known Mass with anticipatedPayload Item EHD efficiency (kg) EHD efficiency (kg) Client payload 5050 Internal systems 20 20 Balloon skin 3,000 714 Balloon support 300 72Thrusters 5,391 129 Scaffolding 539 13 Rectenna 92 22 Helium 1,940 171TOTAL 11,332 1,191 Proposed designs for (left) a balloon craft asdescribed in this embodiment with EHD thrust-mass ratio based on(Masuyama, 2013), compared against (right) an ideal balloon craft withthrusters of superior thrust-mass ratio, conceptually based on Koziellet. al. (Koziell, 2011).

Beyond this embodiment, a reduced craft size employing differentembodiments is physically possible by reducing the mass of specificcomponents. For example, one possible embodiment would utilize an EHDthruster with order-of-magnitude improvement in thrust-mass ratio. Sucha design change would allow for far less thrusters aboard the craft,enabling significant overall mass reduction by following the precedingdesign process. The right column in Table 3 demonstrates this case, witha revised craft mass of only 1,191 kg. Such improvement is possible,given that the MIT thruster (Masuyama, 2013) used in this evaluation wasnot optimized for maximum thrust/mass efficiency and could not generateenough thrust to lift its own weight. Other researchers, however, havedemonstrated that such a craft can support its own weight (Koziell,2011), thereby demonstrating capability of achieving the mass budget inthe right-hand column of Table 3.

Design of Ground Station Parameters

Transmitter area and diameter are found by solving or selecting all thevariables in the equation for beam efficiency (η), the ratio of powerreceived (P_(r)) to power transmitted (P_(t)). The transmitting antennais assumed to have uniform amplitude and phase, and to be correctlyaligned with the receiving antennae (Shinohara, 2014). Real situationsmay vary, requiring more detailed calculations. An examination of therequired design considerations for an appropriate ground system follows.All of the parameters required, along with final values taken, to designthe ground station can be found in Table 4.

TABLE 4 Power Transmission parameters Item Description Value A_(t) totalradiated power from transmitter 44,400 m² P_(r) power needed atreceiving antenna 292 kW n₁ rectenna efficiency 80% (Brown, 1992) η beamefficiency 75% other losses neglected for simplification P_(t) powerfrom transmitting antenna 487 kW (minimum) f transmission frequency 2.45GHz λ transmission wavelength 0.12 m D separation between the apertures25,000 m (balloon altitude) τ beam efficiency coefficient   >2(Shinohara, 2014) p_(d) power density at center of receiving 2,300 W/m²location

Design of Beam and Transmission Efficiency

An important distinction must be made in discussing the efficiency ofthe power transmission system. Beam efficiency used in determining thetransmitter size refers to the ratio of energy reaching the receivercompared to how much energy departed from the transmitter, andrepresents the angular confinement of the radiation pattern. This valueis only a small subset of the total system losses comprising“transmission efficiency” which include atmospheric, system, heat, andother losses including beam efficiency. Both types need to be consideredin a complete design.

Beam Efficiency

Beam efficiency for radio and microwaves in the near-field is foundusing the following experimentally-derived equation (Brown, 1992,Shinohara, 2014):

$\begin{matrix}{\eta = {\frac{P_{r}}{P_{t}} = {1 - {\exp \left( {- \tau^{2}} \right)}}}} & (8)\end{matrix}$

where τ is a unitless placeholder described in detail shortly.

Design of Transmitter Size

Beam efficiency through the air can in theory achieve 100% (excludingatmospheric losses) given a large enough transmitter and receiver with aτ value greater than 2. However, considering the transmission distanceinvolved, the frequencies selected, and the limited area available for areceiving antenna on the balloon, the only remaining method to reducethe size of the transmitting antenna (and thus the burden ofconstruction costs) is by reducing the last remaining factor: the beamefficiency. By relaxing the standard chosen for beam efficiency, some ofthe beam can be allowed to escape beyond the perimeter of the balloon.

A beam which diverges may actually offer an additional advantage in thatit will provide a wider range in which the craft can jostle before beamsteering requires adjustment. Thus relaxing the precision needed forpower aiming will ultimately also ensure greater operational efficiency.Close attention, however, should be paid to the potential consequencesof escaped energy which could reach objects such as spacecraft above thetarget altitude.

Beam efficiency is therefore chosen for the purposes of this embodimentto minimize the final transmitter size. A reasonable value was taken as75%, which means that 25% of the beam will circumvent the targetreceiver. This value does not necessarily constitute a more efficientsystem design, but will nonetheless be used in this embodiment todetermine the size of the transmitter (area and diameter).

TABLE 5 Wireless Power Loss Estimates (based on (McSpadden, 2002)) LossSource Efficiency Comment On Ground DC-microwave 87.5%   Magnetrons,klystrons, etc. (McSpadden, 2002) Magnetron 81.7%   Overall efficiency(McSpadden, 2002) Transmitting 55-73.3%    Phased arrays (Ren, 2006),etc. antenna Through the Air Beam efficiency 75% Selected to reducetransmitter size Cosine (angular) TBD System optimization requiredAtmospheric Negligible Very low for 1-10 GHz (ITU, 2009) Weather 0-20%loss Depend on rain severity (Thiagarajah, 2013) On the Craft Rectenna80% Established technology (Brown, 1984) PMAD TBD System optimizationrequired Step-up voltage 93% Established technology (Liang, 2013)conversion Thruster 25.7 N/kW Established technology (Masuyama,efficiency 2013) TOTAL LOSSES ~55%  Existing designs (McSpadden, 2002)

Design of Total Transmission Efficiency

The factors determining total end-to-end system efficiency are describedin Table 5. Atmospheric losses are minimized when operating in thefrequency range of 1 to 10 GHz. Attenuation is less than 0.01 dB per kmfor oxygen and less than 0.001 dB per km for water, but risessubstantially above that frequency range. Hence, numerous industriesrely on this band of low-GHz frequencies for many Earth-to-Space andSpace-to-Earth applications including radio astronomy and satellitecommunications.

Propagation losses due to inclement weather such as strong rain (“rainfade”) have been well documented elsewhere. Under certain conditions,rain can generate interference of 0.2676 dB per kilometre (Thiagarajah,2013).

Additional loss factors include AC-to-microwave conversion losses, anycosine losses from energy not perpendicularly incident on the rectennaarray, and power management and distribution (PMAD) losses. Each ofthese factors would require an increase to the transmitter size in orderto deliver the same power needed, and will require specific design workby the constructor to optimizing their system.

As an example estimate of total losses, others have proposed a DC-to-DCefficiency of 45% (McSpadden, 2002) for microwave beams used inspace-based solar power (SBSP), the continuous transmission of powerfrom geosynchronous orbit to Earth. Such a transmission system withvastly increased transmission distances would experience losses inexcess of the concept proposed here, but the comparison nonethelessoffers a valuable baseline reference of what total system performancemight be.

Power Frequency Selection

Operation of the system hinges on selecting a desirable frequency forpower transmission. Factors which can contribute to frequency selectioninclude, but are not limited to nor restricted to: transmissionefficiency; atmospheric attenuation; power density; beam width;reception efficiency; total end-to-end DC-to-DC efficiency; complexity;cost; ease of design, construction, production, transportation,assembly, instalment, deployment; operations, maintenance, removal,recovery, disposal, safety, public opinion, and regulation. Frequenciesin any manageable range can be employed which include, but are notlimited to, the visible, UV, IR, near-IR, medium-IR, far-IR, radio, andmicrowave ranges.

Frequencies in the low Gigahertz range (1 through 10 GHz) areparticularly well-suited for power transmission, as they experiencesignificantly lower atmospheric absorption and are thus often used forapplications such as radio astronomy, Earth-based communication, andspace-Earth communication. One viable candidate group of frequencies tobe considered in this embodiment include, but are not limited to, theindustrial, scientific, and medical (ISM) bands, as governed by theInternational Telecommunications Union (ITU) for the use of RF energyintended for applications other than communications. Devices such asmicrowave ovens, cordless phones, military radars and industrial heaterscommonly operate within these bands.

Transmitter

Returning to the matter of calculating the transmitter size based on thechosen beam efficiency of 75%, the unitless placeholder τ from equation8 is evaluated:

$\begin{matrix}{\tau = \frac{\sqrt{A_{t} \cdot A_{r}}}{\lambda \cdot D}} & (9)\end{matrix}$

The value τ is proportional to the surface areas of the transmittingA_(t) and receiving antennae A_(r), and inversely proportional to thetransmission wavelength A and separation distance D. Employing areceiving area of 269 m² based on the above design with an altitude of25 km (transmission distance) and a beam wavelength of 0.12236 metres(based on 2.45 GHz), the transmitting antenna is found to be 44,000 m²,with 237 m diameter. Additional transmitter sizes for variousfrequencies in the ISM bands are presented in Table 6. Transmitter using5.8 GHz offers reduced physical size compared to 2.45 GHz and higherenergy per photon. Increasing the frequency beyond these two optionscould subject the constructor to problems such as regulation issues,higher atmospheric attenuation, and other problems. A transmitter using24.125 GHz offers advantageous physical size with the trade-off ofsignificantly increased atmosphere attenuation.

TABLE 6 Transmitter Sizes Transmission Antenna Antenna Frequency (GHz)Area (m²) Diameter (m) 2.45 44,400 237 5.8 5,700 85 24.125 330 20

Transmitter size can be reduced by adjusting other parameters inequation 9, such as by increasing or decreasing the separation distancebetween craft and ground, thus altering the craft altitude. A differentseparation distance however could subject the craft to greater winddrag, and in so doing require a larger craft to compensate. Ultimately,a lightweight and easily-transportable transmitting antenna may be themost efficient means of maintaining low cost and complexity, rather thana change in transmitter size.

Power Density Considerations

Beam power density can be found with the following equation:

$\begin{matrix}{p_{d} = \frac{A_{t} \cdot P_{t}}{\lambda^{2} \cdot D^{2}}} & (10)\end{matrix}$

The terms from Equation 10 and their values are presented in Table 4.The resultant power density at beam center is 2,300 W/m².

Unfortunately, the ANSI/IEEE standard for maximum permissible humanexposure to microwave radiation at 2.45 GHz is currently a mere 81.6W/m² (8.16 mW/cm²) averaged over six minutes, or 16.3 W/m² (1.63 mW/cm²)averaged over 30 minutes (Lin, 2002). This discrepancy of two orders ofmagnitude in power density is an ongoing challenge faced by alldevelopers of long-distance wireless power transmission. The matter willrequire ongoing collaboration with policy makers and regulatory agenciesto achieve progress. Technological options to avoid transmission throughhumans, animals or objects, was presented above.

Various models exist for distributing power across the transmittingantenna including uniform, Gaussian, Chebyshev, and Taylordistributions. All options require specific information about thetransmitting system, such as total number of antenna elements, and theratio between the power at the center and at the edge of thetransmitting antenna. Further details are provided by Shinohara(Shinohara, 2014).

Transmission Distance Limit

The transmitter may in some cases need to be placed far from the ballooncraft, or the balloon may be required to travel far to perform tasks.The limit of elevation for a phased array antenna is 60 degrees downfrom zenith. A craft positioned 43 km away from the transmitter (grounddistance) could therefore still effectively receive power at itsaltitude of 25 km, albeit requiring a greater amount of power toaccommodate the increased distance from the transmitter.

Greater transmission distance can be achieved by tilting the arraytoward the target, parallel to the ground to provide wireless power tothe craft at 565 km, the same distance as the radius of coverage.Tilting can be performed by designing a rig to rotate the array, or bycreating a permanent scaffold on the ground on which to place the array,among other options. Large phased arrays have been used in this mannerof tilting throughout the world for many decades, notably in militaryapplications for RADAR services.

Increasing separation distance from the power source by any distancewill inherently increase the propagation path, requiring an iterativeapproach to determine new energy beam requirements, and subsequentlycraft size.

Assembly

In this embodiment of the present invention, the balloon skin with theprotrusions is to be fabricated and assembled. The scaffold should beassembled, along with thrusters, and joined to each other. The rectennacan be printed or assembled on its own or as part of the balloon skin.

The scaffold can be joined to the balloon in a development facility orat the deployment location. The client payload should be encased andsecured in the payload cargo hold.

The various components of the balloon train including flight terminationunit, parachute, emergency transponders/beacons, any reflector orparabolic dishes to aid in communication and signal reflection, can beadded to the train at a development facility or on location.

Deployment of Craft

When all components are added to the launch train and secured, and areready for deployment, then the balloon should be filled with therequisite about of helium as per common practice with high-altitudesuperpressure balloons. The balloon will partially inflate atground-level pressure and temperature. In some embodiments, a guideballoon may be placed above the primary superpressure balloon to providelift assistance while the primary balloon inflates and pressurizes. Theprimary balloon (and any proposed secondary balloons) will be released,and the train will follow the balloon up into the sky.

Control of Craft During Ascent

As the balloon ascends, the scaffolds will align vertically beneath it.When all of the thrusters are facing their appropriate directions, thenthe thrusters can be activated to help guide the craft as it ascends.Thrusters can be activated in uniform to achieve flight in a desireddirection, or in countering directions (Left-most thrusters firingforward, while right-most thrusters fire in reverse) to generate arotation. Then all thrusters can fire in the same direction to achieveforward (or reverse) translation. This control mechanism can be used tohelp steer the craft and avoid objects and obstacles while the craftrises to the target altitude.

Operation of Craft at Target Altitude

When the craft reaches target altitude, it can be pre-programmed tomaintain stable geostationary position by registering its position basedon sensors and GPS technology, and firing various thrusters to adjustposition accordingly, to achieve a certain destination, or maintainposition relative to a guide beacon at the ground station. Emergencymeasures were discussed above.

Controlled Landing of the Craft

When a landing is desired, a signal will be sent to the craft from theground station. The antenna and transceiver aboard the craft willreceive the message and transfer it to the CPU. Alternatively, thefollowing will take place in the event that the craft has automaticallyelected to land due to an emergency situation. In both cases, thrusterswill automatically be engaged to rotate the craft and guide it in theappropriate direction, while the balloon lowers itself. Means of balloonlowering can include, but are not limited to, expelling excess gas,either to the environment or into a storage chamber, inner balloon, orgas canister, among other options. In emergency situations, thesuperpressure balloon can be popped and the parachutes deployed to allowthe craft to return to Earth quickly. In either case, the thrusters willprovide lateral steering while the craft descends, in order to helpguide the craft to the desired landing point.

The craft can be brought to a complete landing on ground, or can belowered to a near-landing (a certain distance above the Earth), andretrieved by some means of capturing including, but not limited to:mechanical, magnetic, or other form of harnessing the craft, tetheredand moored at a specific height, if needed. At this point, whether thecraft is grounded or stationary at a set altitude, it can be serviced toenact repair, replacement or upgrade to any of the craft components, theentire craft itself, or the client payload. At this time the craft canbe placed in storage or, upon inspection including all appropriatesafety and regulatory matters, the craft can be prepared for launchagain.

Modification and Variations

Whereas a few specific embodiments of the invention are herein shown anddescribed, it will be evident that variation and modification ispossible. Accordingly, the invention should be understood to be limitedonly by the appended claims, purposively construed.

REFERENCES

-   Binns, W. R. The super-tiger instrument: Measurement of elemental    abundances of ultra-heavy galactic cosmic rays, The Astrophysical    Journal 788 (2014) 18.-   Brooke, Luke. “High altitude LTA platforms: capabilities and    possibilities.” AIAA 5th Aviation, Technology, Integration, and    Operations Conference (ATIO). Arlington, Va.: AIAA, 2005.-   Brown, W. C. Performance characteristics of the thin-film,    etched-circuit rectenna, IEEE, 1984, pp. 365-367.    doi:10.1109/MWSYM.1984.1131793.-   Brown, W. C. Rectenna technology program: Ultra light 2.45 GHz    rectenna 20 GHz rectenna, Tech. Rep. NASA STI/Recon Technical Report    N (mar 1987).-   Brown, W. C. & Eves, E. E. Beamed microwave power transmission and    its application to space, IEEE Transactions on Microwave Theory and    Techniques 40 (6) (1992) 1239-1250. doi:10.1109/22.141357.-   Brown, W. C. The history of wireless power transmission, Solar    Energy 56 (1996) 3-21. doi:10.1016/0038-092X(95)00080-B.-   DoD, U. S. “Global positioning system standard positioning service    performance standard.” Assistant secretary of Defense for command,    control, communications, and intelligence, 4^(th) ed. (2008).-   Elphic, R., Delory, G., Hine, B. P., Mahafiy, P., Horanyi, M.,    Colaprete, A., Benna, M. Noble, S. et al., The lunar atmosphere and    dust environment explorer mission, Space Science Reviews 185    (1-4) (2014) 3-25.-   Gilmore, C. K. & Barrett, S. R. Electrohydro-dynamic thrust density    using positive corona-induced ionic winds for in-atmosphere    propulsion, in: Proc. R. Soc. A, Vol. 471, The Royal Society,    2015, p. 20140912.-   Grass, L. A. Superpressure balloon for constant level flight, Tech.    rep., Air Force Cambridge Research Laboratories, Office of Aerospace    Research, United States Air Force, L. G. Hanscom Field, Mass. 1962.-   ITU Study Group 3. Propagation data and prediction methods required    for the design of earth-space telecommunication systems, P Series,    Tech. rep. (2009).-   Koziell, L., Zhao, L., Liaw, J., & Adamiak, K. Experimental studies    of EHD lifters, in: Proc. ESA Annual Meeting on Electrostatics 2011.-   Kuroda, V. M., Allard, M. R., Lewis, B., Lindsay, M. Comm for small    sats: The lunar atmosphere and dust environment explorer (LADEE)    communications subsystem, 2014.-   Liang, Tsorng-Juu, et al. “Novel isolated high-step-up DC-DC    converter with voltage lift.” IEEE Transactions on Industrial    Electronics 60.4 (2013): 1483-1491.-   Lin, J. C. Space solar-power stations, wireless power transmissions,    and biological implications, Microwave Magazine, IEEE 3 (1) (2002)    36-42.-   Mankins, J. C. The Case for Space Solar Power, Virginia Edition    Publishing, 2014.-   Massa, A., Oliveri, G., Viani, F. & Rocca, P. Array designs for    long-distance wireless power transmission: State-of-the-art and    innovative solutions, Proceedings of the IEEE 101 (6) (2013)    1464-1481. doi:10.1109/JPROC.2013.2245491.-   Masuyama, K., & Barrett, S. R. H. On the performance of    electrohydrodynamic propulsion, Proc. R. Soc. A 469 (2154).    doi:10.1098/rspa.2012.0623.-   McSpadden, J. O. & Mankins, J. C. Space solar power programs and    microwave wireless power transmission technology, IEEE Microwave    Magazine 3 (4) (2002) 46-57. doi:10.1109/MMW.2002.1145675.-   Moreau, E., Benard, N., Lan-Sun-Luk, J. D. & Chabriat, J.-P.    Electrohydro-dynamic force produced by a wire-to-cylinder dc corona    discharge in air at atmospheric pressure, Journal of Physics D:    Applied Physics 46 (47) (2013) 475204.-   Randel, W. J. Global atmospheric circulation statistics, 1000-1 mb,    Tech. rep., National Center for Atmospheric Research, Boulder, Colo.    National Aeronautics and Space Administration, Washington, D.C.    National Science Foundation (February 1992).-   Ren, Y. J. & Chang, K. New 5.8-ghz circularly polarized    retrodirective rectenna arrays for wireless power transmission,    Microwave Theory and Techniques, IEEE Transactions on 54 (7) (2006)    2970-2976.-   Shibata, H., Watanabe, Y., Yano, R. & Suzuki, K. Numerical study on    fundamental characteristics of electro-hydrodynamic thruster for    mobility in planetary atmosphere, in: Transactions of the Japan    society for aeronautical and space sciences, aerospace technology,    Vol. 12, 2014, pp. 5-9.-   Shinohara, Naoki. Wireless power transfer via radio waves. John    Wiley & Sons, 2014.-   Thiagarajah, S. P. The effect of rain attenuation on s-band    terrestrial links, in: 2013 IEEE Symposium on Wireless Technology &    Applications (ISWTA), IEEE, 2013, pp. 192-197.    doi:10.1109/ISWTA.2013.6688768.-   Wathen, R. L. Genesis of a generator—The early history of the    magnetron, Journal of the Franklin Institute 255 (1953) 271-287.    doi:10.1016/0016-0032(53)90388-3.

1. An apparatus having a communications payload and a superpressureballoon adapted to suspend the communications payload at a predeterminedaltitude, the apparatus comprising: electrically-powered thrustersoperatively coupled to the balloon and adapted to provide a forcesuitable to counter winds associated with the predetermined altitude; arectenna suspended by the balloon and adapted to produce electricity topower the thrusters and the payload; and a controller associated withthe payload adapted to control to the thrusters to maintain theapparatus in geosynchronous position above the earth.
 2. The apparatusaccording to claim 1, wherein the thrusters are electrohydrodynamicthrusters.
 3. A system comprising the apparatus of claim 1 and aground-based microwave generator and antenna array adapted to direct amicrowave signal beam to the rectenna.
 4. Use of the system of claim 3to support a communications payload at an altitude of about 25 km.
 5. Asystem comprising: a superpressure balloon; a communications payloadsuspended, in use, by the balloon; electrically-powered thrustersoperatively coupled to and suspended by the balloon; a rectennasuspended by the balloon and adapted to convert wireless wave energyinto electricity; a power means for directing wave energy to therectenna, wherein the power means, thrusters and rectenna are adaptedsuch that, in use, the thrusters provide sufficient force to maintainthe apparatus in geosynchronous position above the earth.
 6. The systemaccording to claim 5, wherein the thrusters are electrohydrodynamicthrusters.
 7. The system according to claim 5 wherein the power means isa ground-based microwave generator and an antenna array adapted todirect a microwave signal beam to the rectenna.
 8. Use of the system ofany one of claim 5 to support a communications payload at an altitude ofabout 25 km